Ecology

ECOLOGY

Ecology is the scientific study of:

organisms in relation to their environment

this includes the relationship of organisms with:

organisms

each other

non-living components of their environment

Temperature affects distribution of vegetation on earth

Polar Temperate Tropic

Polar

TropicTemperate

Predator & Prey interactions

control each other’s population size

Biotic factor living organismse.g. predators, competitors,

parasites

Abiotic factor non-living factors which

influence organisms e.g. light, temperature,

soil, rainfall

Habitat is the particular locality in an environment

in which an organism lives

FOOD

SPACE

WATER

Examples of habitat:

soil burrows (earthworms)

rock pools (limpets, barnacles, top shells)

Population

is the group of individuals of the same species living in a particular area at the same time

Community includes all the

populations of all the species within an ecosystem

Ecosystem is a natural unit composed of living and non-

living components whose interactions result in a stable self-perpetuating system

Or more simply, an ecosystem

is a community of organisms in conjunction with the nonliving components of their environment (things like air, water and mineral soil), interacting as a system

Examples of

ecosystems

pondsan oak treea fielda rockpoolthe sea

Competition for resources can be between individuals of the:

same species Intraspecific competition

Competition for resources can be between individuals of the:

different species

Interspecific competition

Camels, goats and sheep compete for

food.

Question: SEP, 2007

a) Distinguish between intraspecific and interspecific competition. (2)

b) Explain why intraspecific competition is likely to be more intense than interspecific competition. (1)

Members of a species use the same resources but different species use different resources.

c. i) List TWO resources that animals compete for. (2)

space, food, water,mate

ii) List TWO resources that plants compete for. (2)

Space, light, water, ions in soil, carbon dioxide

d) What is the effect of competition on the growth of a population? (1)Reduces the growth rate of a population.

Question: MAY, 2008

Before 1859 there were no wild rabbits in Australia but

in 1859 some domestic rabbits escaped from their

pen, when it was swept away by a flood. These rabbits ran wild and bred at such a rate that parts of Australia soon became overrun with them. The following graph shows

how the population of rabbits increased with time.

a. Describe and explain the growth of the rabbit population at stages 1, 2 and 3. (12)

STAGE 1:Slow increase in population.Few individuals able to reproduce.Rabbits need to acclimatise. STAGE 2:Rapid increase in population.Many individuals able to reproduce.Resources are abundant.

a. Describe and explain the growth of the rabbit population at stages 1, 2 and 3. (12)

STAGE 3:Population stable.Resources become limited and can support a certain number of individuals.

b. Discuss the effect of the observed growth rate of rabbits on agricultural activity in Australia. (2)Rabbits fed upon crops and caused damage to agriculture.c. Suggest how the observed growth rate of rabbits affected the natural ecosystem in Australia. (2)Many wild plants were eaten leading to loss of plant species, more soil erosion as soil was no longer covered by vegetation.

An ecosystem consists of three nutritional groups:

a) PRODUCERS

b) CONSUMERS

c) DECOMPOSERS

–autotrophic plants

–heterotrophic organisms, mainly animals

– saprophytic bacteria & fungi– break down dead matter to

return nutrients to the soil

Question: SEP,2012

Distinguish between producers and consumers.(4)

Question: MAY,2011

Distinguish between a community of plants and a population of plants. (2)

Niche is the role or job of an organism within the

community

Food chains

Food chains show: the movement of food energy from one

organism to the next

PRODUCER PRIMARY CONSUMER

SECONDARY CONSUMER

TERTIARY CONSUMER

1st Trophic level

2nd Trophic level

3rd Trophic level

4th Trophic level

Trophic level = feeding level

Top carnivore

Ecosystem: Field

hawk sparrow rcaterpilla leaves

Ecosystem: Oak tree

Ecosystem: Freshwater pool

thrush larvaeinsect oak tree

le waterbeet tadpolealgae

ladybird aphid grass

FOOD WEBS are made up of many food

chains linked together give a more complex

picture of how animals feed

are more stable than food chains

In the food web shown:

1. There are …… primary consumers.

2. The top carnivore is the ……… .

5

owl

3. Suppose all the woodmice died from a poison,

i) the acorn would (increase / decrease).

3. Suppose all the woodmice died from a poison,

i) the acorn would (increase / decrease).

3. Suppose all the woodmice died from a poison,

i) the acorn would (increase / decrease).

ii) the weasel would (increase / decrease).

3. Suppose all the woodmice died from a poison,

i) the acorn would (increase / decrease).

ii) the weasel would (increase / decrease).

4. Draw a food chain with 5 links from this food web.

5. In this food web, the shrew can be either a ………………. or a ……………….. consumer.

owloak leaf greenfly ladybird shrew

secondary tertiary

Question: MAY, 2004

The following organisms can be found in the same habitat:

weasel, rabbit, greenfly, green plant, caterpillar, small bird and ladybird.

Construct a food web to include all the organisms found in the list above.

green plant

ladybird

rabbit greenfly caterpillar

weaselsmall bird

weasel, rabbit, greenfly, green plant, caterpillar, small bird and ladybird

Weasel eats small mammals & birds.

PYRAMIDS

Three types of pyramid:

a) Pyramid of Numbers b) Pyramid of Biomass c) Pyramid of Energy

a) Pyramid of Numbers

shows the total number of individuals at each trophic level

a) Pyramid of Biomass

indicates the weight of all individuals at each trophic level

biomass is the weight of living material

Draw a pyramid of numbers & of biomass for this food chain:

Pyramid of Numbers

Rosebush Aphid Ladybird

Pyramid of Biomass

RosebushAphid

Ladybird

Question: SEP, 2012From the food web write a food chain including four trophic levels. (2)

[Any food chain as long as 4 trophic levels are present]

b) In the space below draw a pyramid of numbers for the food chain you answered in ‘a’. (In your diagram label each trophic level).

(3)

a) Pyramid of Energy

shows the transfer of energy from one trophic level to the next

90% loss in energy at EACH trophic level

Pyramid of Energy

Energy is lost in:1. excretion2. moving about3. keeping the

body warm4. egestion5. respiration

Question: SEP, 1996

Give a reason why the number of trophic levels seldom exceeds 5. (1)

Great (90%) losses in energy at every trophic level.

Question: SEP, 1996

Approximately what percentage of all the energy present at one trophic level is transferred to the next higher trophic level? (1)

Only 10% of the energy is transferred to the next trophic level.

Question: MAY, 1999

Why is energy not recycled in ecosystems?(1)

Lost as heat to the surrounding environment.

Compare flow of energy & flow of nutrients in ecosystems:

Flow of ENERGY is LINEAR but flow of NUTRIENTS is CYCLIC.

SUNLight

energy

Bioticcomponent

Heat

energy

Abioticcomponent

nutrients

ENERGY FLOW

SHORTENING THE FOOD CHAIN the shorter the food chain, the more people

can be fedREASON: the 90% ‘wastage’ of energy that occurs between each trophic level is cut down

Why do leaves look green?

Green light is reflected by the leaf.

ENERGY FLOW THROUGH PRODUCERS

Only 1% of the light falling on a leaf is used in photosynthesis. What happens to the rest?

30% evaporates water from plant

20% is reflected from plant

40% warms up soil, air and vegetation [transmitted]

The chemical energy built by the plant is

used by the plant for:1. Respiration2. Growth

The energy used for: respiration :

is not available for the next trophic level

growth:is passed on the next trophic level

ENERGY FLOW THROUGH CONSUMERS

over half of the energy in the grass the cow eats, is passed out of the body in faeces

Absorption by living

things

Decomposition by bacteria and fungi

NUTRIENT CYCLING

Excretion and death

Nutrients in living

organisms

Nutrients in environment available for

use

Nutrients in dead bodies and waste

all living things need carbon to make: carbohydrates fats proteins

The Carbon Cycle

Processes that :

1. Respiration2. Decomposition3. Combustion

1. Photosynthesis

CO2 in air

0.03%ADD: REMOVE:

The Carbon Cyclecarbon dioxide

gas

carbon compoundsin animals

carbohydrates ingreen plants

carbo n co mpo u nd sin de ad o rg an ic matte r

(hu mus)coal

death fossilisationdeath

photosynthesis

plantrespiration combustion

animalrespiration

animalnutrition

decay

1) More fossil fuels are being burnt than in the past.

2) Large areas of forest are being removed and so less CO2 is removed from the air.

The average CO2 concentration in the air is increasing. Give two reasons for this.

How can the greenhouse effect be:1) an advantage to plants? Plants grow more as photosynthesis increases due to a higher temperature.

CO2 is a greenhouse gas: causes warming of atmosphere

2) a disadvantage to plants? More chances to wilt as more water is lost by evaporation.

plants & animals need nitrogen to make: proteins

The Nitrogen Cycle

Nitrogen 78%

plants cannot use atmospheric nitrogen

Gases in air.

From where do plants get the nitrogen they

need?

From the SOIL Mention THREE ways by

which these ions can end up in the soil.

2. Burning fossil fuels (generates nitric oxide)

1. Erosion

3.

Processes that :

1. Lightning2. Nitrogen-fixing

bacteria3. Nitrifying bacteria

1. Absorption by plants2. Leaching3. Denitrifying bacteria

Nitrates in soil

ADD: REMOVE:

The Nitrogen Cycle

NITROGEN(in the air)

Nitrogen-fixing bacteria

Denitrifyingbacteria

SOILNITRATES

lightning

Plant protein

Animal protein

AMMONIA

Dead organisms and faeces

NITRITES

Nitrifyingbacteria

Nitrifyingbacteria

taken upby plants

decompositionexcretion

LIGHTNING causes N2 & O2 to combine at high

temperatures and nitrogen oxides form these oxides are washed into the soil

by rain where they form nitrates

Process that add nitrates to soil

O2 & N2: most abundant gases in air.

NITROGEN-FIXING BACTERIA absorb nitrogen gas from the air and ‘fix’ it into a

form which the plant can use to build protein

change nitrogen gas into ammonium compounds

Root nodule full of bacteria.

NITROGEN-FIXING BACTERIA live:

Root nodules

1) freely in the soil e.g. Clostridium2) in the root nodules of leguminous plants

(e.g. peas, beans, clover) e.g. Rhizobium

Mutualism: is the relationship between nitrogen fixing

bacteria and leguminous plants

Plant gains:Ammonium compounds

Bacteria gain:1. Food2. Shelter

carbohydrate

N

SYMBIOSIS: is a relationship between two organisms

MUTUALISM: is a type of symbiosis is a close relationship between two different

organisms where both benefit from each other

When leguminous plants decay: the nitrogen which the bacteria have fixed

goes into the soil where it can be used by plants

Nitrogen-fixing bacteria are very useful because they increase the amount of useful

nitrogen compounds in the soil.

Leguminous plants:

1.can live in soils poor in nitrates

2.are used in crop rotation to increase nitrates in soil

Clover

Beans

Peas

NITRIFYING BACTERIA change ammonia into nitrites and then into

nitrates this is called nitrification ammonia is present in:

dead remains animal waste

Production of nitrates from organic nitrogen involves decay and nitrification

nitrate

nitrite

ammonia

Organic nitrogen in dead bodies or

animal wasteDecay

Nitrification

Nitrification

Nitrobacter

Nitrosomonas

Bacillus

1) Absorption by plantsroot hairs provide a large

surface area for absorption

salts are absorbed by: diffusion active transport

Three processes remove nitrates from the soil

2) Leachingis when salts are lost

from the soil and reach the groundwater

Nitrates

3) Denitrifying bacterialive in water-logged soilcarry out denitrification by changing

nitrates into nitrogen gase.g. Pseudomonas

Why do farmers dig up the land?To improve drainage and aeration

thus denitrification does not occur.

Distinguish between nitrification and denitrification. (5)

Nitrification is carried out under aerobic conditions but denitrification under anaerobic conditions.In the process of nitrification, ammonia is converted into nitrites and then into nitrates.In denitrification, nitrates are converted into nitrogen gas.

Question: SEP, 2011

The Water Cycle

Question: SEP, 2011

During a fieldwork activity a biology student used a pitfall trap for sampling animals.The diagram above shows the pitfall trap.a) List ONE advantage and ONE disadvantage of this method. Advantage: cheap; easy to set up; no maintenance needed; animals remain alive (1) Disadvantage: animals eat each other; flooding of pitfall trap if it rains (1)

The photo below shows a student using another sampling technique.

The photo below shows a student using another sampling technique. a) Name the piece of apparatus being used to

sample plant density and diversity in the field. (1)Quadrat

The following photo shows three biology students during fieldwork in a woodland area.

Explain why the sampling equipment shown in the diagram cannot be used for animals. (1)

Animals move out of the quadrat and so cannot be counted.

Question: SEP, 2013

THE END